New customer with a third party Draytek Vigor 130 modem and Asus AC5300 router

[#1]

Hi All,

I am joining plusnet on the 12th of March and wanted some advice prior to switching from BT.

I totally understand and know what to do once my line is switched to plusnet with regard with username, password and PPPOE within my Asus AC5300 router, although I have read some conflicting information with regard the set up of my vigor 130 modem and router.

all the advice out there states you should have a MTU of 1492 set within your router, however should this figure be replicated within you modem as nowhere does is say what should be set in an external modem as to be fair the majority of people are using old BT Huawei or ECI modems.

I guess someone will say it does not matter; just make sure the router MTU is set to 1492, however previously my vigor 130 had a MTU of 1520 and 1500 with no apparent issues, however when I replicate the MTU in both the modem and router to 1492 there was a small increase in download speed (+2mb)

Can anyone shed any light on this issue?

Thanks and by the way I am a returning customer to plusnet having only switched to BT as they were the only ISP offering fibre many years ago.

Thanks   

[#2 · Accepted solution]

Have a read of this - https://support.aa.net.uk/MTU 

I use a Vigor 130 and am able to get my Plusnet FTTC broadband line to achieve the maximum 1500 MTU.

To do this, I've set the MTU in both the Vigor 130 modem and my router (pfSense) to 1508 to account for the 8 byte overhead used for PPPoE signalling between the modem and router (which is why old/useless routers that can only handle a maximum WAN interface MTU of 1500 end up only achieving 1492 line MTU).

Theoretically you should be a be able to set higher MTU values (such as the Vigor 130's maximum 1520), but when the PPPoE session is being established, the maximum achievable MTU is negotiated with the FTTC cabinet - which is typically either 1492 or 1500 - depending on your modem and router's support for "Baby Jumbo Frames"

These are my settings -

[#3]

For testing the actual MTU that your router negotiated with the FTTC cabinet,  rather than use terminal ping commands to work out the maximum unfragmented MTU, there is a handy website that automates the test -

http://www.letmecheck.it/mtu-test.php 

Just be aware that this test remotely pings your WAN address and expects the appropriate ICMP response - which I understand recent Plusnet supplied routers are apparently incapable of doing 🙄 !, but otherwise should work perfectly on almost any third party routers 😀.

[#4]

It's fair to say that's one of the best and informative answers I've received via the community and even with screenshots to boot!!
Thanks very much I'll give the MTU's a tweak over the weekend while I'm still with BT.
Roll on my switch over!!! 👏🏼👏🏼👏🏼😂

[#5]

It is probably worth checking that your Vigor 130 is installed with the most up to date firmware (3.8.4.1_BT).

https://www.draytek.co.uk/support/downloads/vigor-130 

Check your router firmware is also the latest and greatest, as enhanced MTU support is sometimes added as an afterthought in subsequent updates, after the initial factory installed firmware version ships.

Like you say, it would be worth optimising your MTU on your existing setup (especially with known to be current firmware), and then you can check the before and after performance of your BT to Plusnet migration.

Good luck !  😉

[#6]

Yeah had the upto date firmware for a while now on the vigor, including Merlin's firmware on the Asus.
Just noticed that my Asus will only support a MTU of 1500, so I'll have to stick with that I guess.
I have noted that the above screenshot has pppoa, is that correct?

[#7]

And another thing !

I'd be interested to see your before and after migration results for the DSLReports speedtest BufferBloat test -

http://www.dslreports.com/speedtest 

- as some Plusnet customers have issues with BufferBloat, and it would be useful to know whether that (not commonly checked) test result changes when migrating from BT (which theoretically should have comparable performance).

You should get a result that looks like -

[#8]

Here are my BT results

[#9]

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@mszune wrote:
I have noted that the above screenshot has pppoa, is that correct?

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That greyed out section (showing the "PPPoA") is as it says at the top, for "DSL Modem Settings (for ADSL mode only)",  so those settings are not relevant when operating in FTTC mode.  The point of including that screenshot was to illustrate that I have the "PPPoE/PPPoA Client" set to "Disable" when operating in "MPoA" "Bridge Mode" as shown in the second picture.

I had my Vigor 130 simultaneously loaded with settings for both ADSL (user selected PPPoA) and for FTTC (PPPoE by default), so when my line was upgraded from ADSL2+ to FTTC VDSL2, the Vigor 130 automatically switched to the new settings, and I didn't notice the transition even though I was listening to a streaming radio station at the time !

[#10]

Just out of curiousity, I have had infinity 2 for some time and regularly achieved downloads over over 70mb, although only recently noticed that my line has been banded as what they tell me.

Having looked at my line stats and trying to work out what is going on, here seems to be a lot leading toward an issue on the far end, what is the far end the cabinet?

[#11]

Moderators Note
This topic has been moved from Fibre Broadband to My Router.

[#12]

Woke up this morning to find that my line stats have altered significantly for the download from 54.995mb to 73.993mb and an SNR of 15db down to 9db. I change a couple of things yesterday, one was to ensure my modem and router had an MTU of 1500 as per the advice given by @Anonymous (Thanks 👍) and the second was to relocate the vigor 130 from its existing location (resting on top of the AC5300) to approximately a metre away with a cat 8 cable.

The upload speed has not changed that is stuck at 16.994mb, although what I do find odd is while my line stats have changed the speed from the Router end have not altered, does this mean I need to reboot both the modem and router by leaving them off for 30mins to re-sync the new line stats altered by DLM?

here's a before (Friday) and after (Sunday) screenshot of my line stats.14921500

[#13]

I'm sure I read somewhere that the vigor 130 doesn't resync with a new line stat once DLM has altered to a new and faster speed, Anyways both router and modem were switched off this morning for 30mins and my download speed now mimics my line stats.

Thanks very much@Anonymous for your help understanding what MTU settings are required within both the router and modem as this has helped significantly and will aid in the transition from BT to Plusnet on the 12th of March. 👏👍

[#14]

Here's my new line stats with BT before I submit this thread as resloved and switch to Plusnet on the 12th of March 2021.

Cheers

[#15]

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@mszune wrote:

I'm sure I read somewhere that the vigor 130 doesn't resync with a new line stat once DLM has altered to a new and faster speed

Other than the few occasions when my line has got banded causing DLM to get stuck (until manually reset),  my Vigor 130 does re-sync (usually around 2am) when DLM has moved the "Attainable Rate" sync speed up or down a meg or two - usually because the weather has changed for better or worse.

Here is an example of my ping graph when DLM has caused a modem re-sync around 2am, the re-sync shown as the red spike indicating packet loss -